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See detailPreparation of drug-loaded scaffolds for biomedical applications using supercritical carbon dioxide technology
Champeau, Mathilde; Jérôme, Christine ULg; Tassaing, Thierry

Conference (2012, March 25)

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See detailPreparation of drug-loaded scaffolds for biomedical applications using supercritical fluid technology
Champeau, Mathilde; Jérôme, Christine ULg; Tassaing, Thierry

Conference (2013, March 17)

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See detailPreparation of fire-resistant poly(styrene-co-acrylonitrile) foams using supercritical CO2 technology
Urbanczyk, Laetitia ULg; Bourbigot, Serge; Calberg, Cédric ULg et al

in Journal of Materials Chemistry (2010), 20

This work deals with the preparation and characterization of fire-resistant poly(styrene coacrylonitrile) (SAN) foams containing (organo)clays and/or melamine polyphosphate (MPP) as fire retardants using ... [more ▼]

This work deals with the preparation and characterization of fire-resistant poly(styrene coacrylonitrile) (SAN) foams containing (organo)clays and/or melamine polyphosphate (MPP) as fire retardants using supercritical CO2 as the foaming agent. The additives dispersion was first characterized with X-ray and transmission electron microscopy (TEM) analyses. Their presence clearly affected the cellular morphology, as observed by scanning electron microscopy (SEM). Then, the peak of heat release rate (PHRR) and total heat evolved (THE) were determined with a cone calorimetry test, performed on each foamed sample as a function of the foam density. Incorporation of clay (3 and 5 wt%) in the exfoliated state into the SAN foam clearly led to a significant decrease of PHRR, while intercalated and aggregated clay had a lower effect. Similar results were obtained with 10 and 20 wt% of MPP. The best results were obtained when exfoliated clay and MPP were combined, with a PHRR drop as large as 75%, thanks to the synergistic action of both additives. The magnitude of PHRR drop, related to the fire resistance, was found to be in direct relationship with the cohesiveness of the protective carbonaceous layer formed at the sample surface during combustion. Clay and MPP, when added together, are thus believed to favour the formation of a highly cohesive protective layer able to act as an efficient shield against the flame, despite the fact that the sample is originally composed of ~90% of voids. [less ▲]

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See detailPreparation of functionalized alkoxyamine initiator and its use
Detrembleur, Christophe ULg; Gross, Thomas; Meyer, Rolf-Volker

Patent (2004)

A one-pot process for the preparation of functional alkoxyamines of the general formula (I),is disclosed. The process entails (1) reacting an oxidizing agent with a sterically hindered secondary amine to ... [more ▼]

A one-pot process for the preparation of functional alkoxyamines of the general formula (I),is disclosed. The process entails (1) reacting an oxidizing agent with a sterically hindered secondary amine to produce an aqueous phase and a nitroxyl radical (2) removing the aqueous phase and adding to the nitroxyl radical one or more vinyl monomer(s) conforming to a formula and a system which produces free radicals. Also disclosed is a process of polymerizing monomers using the functional alkoxyamine. [less ▲]

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See detailPreparation of functionalized alkoxyamine initiator and its use
Detrembleur, Christophe ULg; Gross, Thomas; Meyer, Rolf-Volker

Patent (2003)

A one-pot process for the preparation of functional alkoxyamines of the general formula (I), is disclosed. The process entails (1) reacting an oxidizing agent with a sterically hindered secondary amine to ... [more ▼]

A one-pot process for the preparation of functional alkoxyamines of the general formula (I), is disclosed. The process entails (1) reacting an oxidizing agent with a sterically hindered secondary amine to produce an aqueous phase and a nitroxyl radical (2) removing the aqueous phase and adding to the nitroxyl radical one or more vinyl monomer(s) conforming to a formula and a system which produces free radicals. Also disclosed is a process of polymerizing monomers using the functional alkoxyamine. [less ▲]

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See detailThe preparation of functionalized alkoxyamine initiator and its use
Detrembleur, Christophe ULg; Gross, Thomas; Meyer, Rolf-Volker

Patent (2003)

A one-pot process for the preparation of functional alkoxyamines of the general formula (I), (See Formula I) is disclosed. The process entails (1) reacting an oxidizing agent with a sterically hindered ... [more ▼]

A one-pot process for the preparation of functional alkoxyamines of the general formula (I), (See Formula I) is disclosed. The process entails (1) reacting an oxidizing agent with a sterically hindered secondary amine to produce an aqueous phase and a nitroxyl radical (2) removing the aqueous phase and adding to the nitroxyl radical one or more vinyl monomer(s) conforming to a formula and a system which produces free radicals . Also disclosed is a process of polymerizing monomers using the function al alkoxyamine. [less ▲]

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See detailPreparation of highly ordered CMI-1 and wormhole-like DWM mesoporous silica catalyst supports using C 16(EO) 10 as surfactant
Léonard, Alexandre ULg; Blin, J.-L.; Su, B.-L.

in Studies in Surface Science and Catalysis (2002), 143

Concentrations of polyoxyethylene alkyl ether surfactants located in the hexagonal H1 micellar domain typically afford disordered mesoporous structures of wormhole-like channels after polymerization of ... [more ▼]

Concentrations of polyoxyethylene alkyl ether surfactants located in the hexagonal H1 micellar domain typically afford disordered mesoporous structures of wormhole-like channels after polymerization of the inorganic precursor in solution. The effect of hydrothermal treatment duration and temperature on the characteristics of the obtained disordered DWM (Disordered Wormhole-like Mesostructure) compounds has been investigated. Thermal stability of these samples has also been studied and appears to be superior to that of MCM-41 type materials. If the weight percentage of surfactant in solution is however decreased, well-ordered hexagonal CMI-1 can be directly obtained. In this case, a co-operative mechanism leading to spherical particles of organized channel structures has been proposed. Influence of the surfactant concentration on the arrangement has been discussed in detail. [less ▲]

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See detailPreparation of living polymer microspheres by dispersion atom transfer radical polymerization in scCO2 using fluorinated macroligands
Grignard, Bruno ULg; Calberg, Cédric ULg; Jérôme, Christine ULg et al

Poster (2009, May 19)

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical ... [more ▼]

Due to an increasing need for polymers with well-defined architecture (diblock-, graft-, star-shaped copolymers), molecular weight and/or functional end-groups, the use of controlled radical polymerization (CRP) in scCO2 has started to gain attention. Among all the controlled processes, Atom Transfer Radical Polymerization has emerged as a robust tool for the preparation of polymers with well-defined molecular weight, architecture and chain-end functionality. In a very recent paper, we reported the first efficient dispersion ATRP of methyl methacrylate (MMA) in scCO2 using a fluorinated polymeric ligand that had a dual role, i.e., the complexation of the copper salt and the stabilization of PMMA growing particles. In this contribution, we extended this new system to the dispersion ATRP of styrene, to the synthesis of diblock copolymers beads and the controlled synthesis of hyperbranched copolymers. Finally, because both ATRP and alkyne-azide Huisgen’s 1,3-dipolar cycloaddition relies on the use of a Cu(I) catalyst, synthesis of pyrene end-functionalized polymers by simultaneous dispersion ATRP and click reaction was also investigated in supercritical carbon dioxide. [less ▲]

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See detailPreparation of low-density xerogels by incorporation of additives during synthesis
Alié, Christelle ULg; Ferauche, Fabrice; Pirard, René ULg et al

in Journal of Non-Crystalline Solids (2001), 289(1-3), 88-96

Low-density xerogels were prepared by incorporation of an additive to alcogels prior to gelation. The additives studied are 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS), 3 ... [more ▼]

Low-density xerogels were prepared by incorporation of an additive to alcogels prior to gelation. The additives studied are 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS), 3-aminopropyltrimethoxysilane (AMS), propyltrimethoxysilane (PMS), tetramethylorthosilicate (TMOS) and 3-aminopropyltriethoxysilane (AES) using tetraethylorthosilicate (TEOS) as main silica precursor. Samples were also prepared with EDAS as additive and TMOS as main silica reagent. When the additive contains methoxy groups, it reacts first, forms nuclei on which the main reagent TEOS reacts to form the silica particles. The nucleation mechanism by the additive occurs only in case of a difference of reactivity between additive and main silica precursor. The other group of the additive (amine, alkyl group, ...) influences only the gelation time. In case of ethoxy groups (series AES/TEOS) or methoxy groups (series EDAS/TMOS) for both additive and main reagent, there is no nucleation by the additive. (C) 2001 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailPreparation of low-density xerogels from mixtures of TEOS with substituted alkoxysilanes. I. O-17 NMR study of the hydrolysis-condensation process
Alié, Christelle ULg; Pirard, Jean-Paul ULg

in Journal of Non-Crystalline Solids (2003), 320(1-3), 21-30

Low-density xerogels were synthesised by incorporation of an additive to base catalysed tetraethylorthosilicate (TEOS) alcogels directly during the preparation of the sol. The nucleation mechanism by the ... [more ▼]

Low-density xerogels were synthesised by incorporation of an additive to base catalysed tetraethylorthosilicate (TEOS) alcogels directly during the preparation of the sol. The nucleation mechanism by the additive was established by experiments during sol-gel transition. O-17 NMR spectroscopy on TEOS-ethanol-water, 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS)-ethanol-water and EDAS-TEOS-ethanol-water solutions shows that the hydrolysis-condensation of EDAS is much faster than that of TEOS. Consequently it can be assumed that EDAS forms nuclei, onto which TEOS condenses later to form the silica particles. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailPreparation of low-density xerogels from mixtures of TEOS with substituted alkoxysilanes. II. Viscosity study of the sol-gel transition
Alié, Christelle ULg; Pirard, René ULg; Pirard, Jean-Paul ULg

in Journal of Non-Crystalline Solids (2003), 320(1-3), 31-39

Mixtures of TEOS with substituted methoxysilanes generate low-density xerogels due to a nucleation mechanism involving the substituted alkoxysilane. The sol-gel transition of these mixtures was followed ... [more ▼]

Mixtures of TEOS with substituted methoxysilanes generate low-density xerogels due to a nucleation mechanism involving the substituted alkoxysilane. The sol-gel transition of these mixtures was followed by theological characterisation. The transition from sol to gel takes place in a few minutes at ambient temperature. For the series exhibiting nucleation by the additive. the gel time goes through a slight minimum when the ratio of additive/main reagent increases. The elastic modulus increases with increasing ratio of additive/main reagent as the particle size decreases because of the nucleation mechanism by the additive. Samples with smaller particles exhibit the highest modulus for equal silica concentrations. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailPreparation of low-density xerogels through additives to TEOS-based alcogels
Alié, Christelle ULg; Pirard, René ULg; Lecloux, A. J. et al

in Journal of Non-Crystalline Solids (1999), 246(3), 216-228

A new process for preparing silica xerogels with similar textural properties to silica aerogels by drying under vacuum has been studied. The xerogels are produced by adding, before gelation, 3-(2 ... [more ▼]

A new process for preparing silica xerogels with similar textural properties to silica aerogels by drying under vacuum has been studied. The xerogels are produced by adding, before gelation, 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS) to tetraethylorthosilicate (TEOS)-based alcogels, synthesised in a single base-catalysed (NH3) step. It is hypothesized that EDAS acts as a nucleation agent leading to silica particles with a hydrolysed EDAS core and a shell principally made of hydrolysed TEOS. The EDAS concentration and the basicity of the aqueous NH3 solution are important parameters influencing the resistance of the gel to drying stress. A decreasing EDAS/TEOS ratio or an increasing concentration of NH3 at constant EDAS content leads to less shrinkage during drying and so the final pore volume is larger. Gels prepared with a low EDAS/TEOS ratio (about 0.03) contain large particles (similar to 20 nm) due to the nucleation process by EDAS, thus the pores between those particles are also large and the drying stress is reduced. (C) 1999 Published by Elsevier Science B.V. All rights reserved. [less ▲]

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See detailPreparation of macroporous biodegradable poly(L-lactide-co-epsilon-caprolactone) foams and characterization by mercury intrusion porosimetry, image analysis, and impedancy spectroscopy
Maquet, Véronique; Blacher, Silvia ULg; Pirard, René ULg et al

in Journal of Biomedical Materials Research (2003), 66A(2), 199-213

Two poly(L-lactide-co-epsilon-caprolactone) random copolymers containing 5 and 40 mol% of epsilon-CL, namely P(LA-co-CL5) and P(LA-co-CL40), respectively, have been made macroporous by freeze-drying ... [more ▼]

Two poly(L-lactide-co-epsilon-caprolactone) random copolymers containing 5 and 40 mol% of epsilon-CL, namely P(LA-co-CL5) and P(LA-co-CL40), respectively, have been made macroporous by freeze-drying solutions in dimethylcarbonate. Most of the freeze-dried foams, prepared by varying polymer concentration and cooling rate, exhibited two main pore populations: (1) longitudinally oriented tube-like macropores with diameters greater than or equal to100 mum, and (2) interconnected micropores (10-100 mum). Pore characteristics, including macropore density, mean diameter, and interdistance, as well as micropore density, area, and shape, were determined by image analysis of scanning electron micrographs in order to study the influence of processing and formulation parameters on foam structure and properties. The pore orientation and the 3-D texture also were studied by image analysis and impedance spectroscopy. In the case of the P(LA-co-CL5), the macropore diameter increased with the cooling rate while the micropore diameter decreased. The micropores also became more circular when the cooling rate was increased. The pore size and morphology of the P(LA-co-CL40) were quite unchanged by varying the cooling rate. All the other conditions being the same, the P(LA-co-CL5) foams were better organized than the P(LA-co-CL40) foams, and pore orientation was improved at the higher cooling rate. Pore size and morphology also can be controlled by changing the polymer concentration (Cp), as we showed by studying P(LA-co-CL5) foams prepared by freeze-drying solutions in the 1-10 w/v% Cp range. Macropore density, average diameter, and interdistance of P(LA-co-CL5) foams increased with Cp, but the micropore characteristics remained almost unchanged no matter the Cp. The reliability of the characterization methods has been discussed, with special attention to mercury intrusion porosimetry, which is used primarily for measurement of pore volume and pore size distribution. However, this technique is reported here as a destructive and unreliable method for the characterization of fragile P(LA-co-CL40) foams. This study shows that image analysis and impedance spectroscopy can give reliable information relative to the pore morphology and anisotropy of freeze-dried foams. [less ▲]

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See detailPreparation of mebendazole HP-b-cyclodextrin complexes using water soluble polymers and organic acids
Alvarez, Covadonga; Van Hees, Thierry ULg; Piel, Géraldine ULg et al

Conference (2000, April)

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Peer Reviewed
See detailPreparation of mebendazole HP-beta-cyclodextrin complexes using water-soluble polymers and organic acids
Alvarez, Covadonga; Van Hees, Thierry ULg; Piel, Géraldine ULg et al

in STP Pharma Sciences (2001), 11(6), 439-442

Mebendazole (MBZ) is a carbamate derivative with an aminobenzimidazole structure. It possesses antihelminthic properties and is particularly insoluble in water. In order to increase its aqueous solubility ... [more ▼]

Mebendazole (MBZ) is a carbamate derivative with an aminobenzimidazole structure. It possesses antihelminthic properties and is particularly insoluble in water. In order to increase its aqueous solubility, hydroxpropyl-beta-cyclodextrin (HP-beta-CD) was used in combination with water-soluble polymers (polyvinylpyrrolidone or hydroxypropymethyl cellulose) and different organic acids (citric or tartaric). Increased solubility was observed on heating the mixture. The effects of the time and temperature of the heating process on drug solubility and stability were investigated. The results clearly show that the best conditions for increasing solubility and limiting degradation of MBZ is to heat a combination of MBZ, HP-beta-CD (200 mM), tartaric or citric acid (50 mM) and HPMC (0.1% w/v) in a water-bath at 95degreesC for 60 min. This method increases solubility to about 680 mug/ml and limits degradation to 2.5%. [less ▲]

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See detailPreparation of multilayered chitosan-based nanofibers by combination of electrospinning and layer-by-layer deposition techniques
Croisier, Florence ULg; Aqil, Abdelhafid ULg; Detrembleur, Christophe ULg et al

Poster (2009, March)

By combining electrospinning technique and layer-by-layer deposition, we produced a new material made of multilayered, chitosan-based nanofibers. Layer-by-layer (LBL) is a well known method for surface ... [more ▼]

By combining electrospinning technique and layer-by-layer deposition, we produced a new material made of multilayered, chitosan-based nanofibers. Layer-by-layer (LBL) is a well known method for surface coating, based on electrostatic interactions. It enables the controllable deposition of a variety of polyions including synthetic and natural materials, with designable layer structure, defined wall thickness and size. Electrospinning (ESP) technique allows the fabrication of polymer fibers ranging from nanometers to a few microns in diameter, depending on the polymer characteristics (a.o. molecular weight, solution viscosity and conductivity) and processing conditions (electric potential, distance between syringe-capillary and collection plate, concentration, flow rate) (3). Mats of nanofibers produced by ESP display a very large surface area-to-volume ratio and high porosity with very small pore size. The nanometric scale of electrospun fibers also proves a positive effect on cellular growth, as fibers mats mimic extracellular matrix structure. The association of these two techniques with the use of biocompatible and biodegradable polymers such as chitosan, gives outstanding prospects in the field of biomedical applications, especially for the preparation of wound dressings, artificial skin or tissue engineering scaffolds. In the present study, a charged copolymer, poly(methylmethacrylate-block-methacrylic acid), was added to a poly(ε-caprolactone) or poly(D,L-lactide) solution before electrospinning in order to obtain charges on fibers surface. Oppositely charged polyelectrolytes – chitosan and poly(styrene sulfonate) or hyaluronic acid – were then alternately deposited on these aliphatic polyester fiber “cores” using LBL method. The aliphatic polyester core was also removed selectively to confirm the existence of a multilayered shell, obtaining hollow fibers. [less ▲]

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See detailPreparation of nanosized barium zirconate powder by precipitation in aqueous solution
Boschini, Frédéric ULg; Guillaume, Bernard ULg; Rulmont, André ULg et al

in Key Engineering Materials [=KEM] (2004), 264-268(Part 1-3), 2335-2338

Several ways were explored to synthesize barium zirconate by soft chemistry methods in aqueous solution. In the first method the synthesis of barium zirconate was initiated by urea decomposition, through ... [more ▼]

Several ways were explored to synthesize barium zirconate by soft chemistry methods in aqueous solution. In the first method the synthesis of barium zirconate was initiated by urea decomposition, through an homogeneous precipitation of barium and zirconium salts followed by a "low temperature" thermal treatment. The kinetic of the reaction and the optimum urea/cation ratio have been determined by means of X-ray diffraction and Inductive Coupled Plasma analyses. It has been demonstrated that an amorphous zirconium hydrated oxide starts to precipitate followed by the precipitation of barium carbonate[1]. A calcination at 1200degreesC during 2 hours gives rise to the formation of a pure barium zirconate phase. In the other methods, barium zirconate was synthesized, in one step without any thermal treatments, by precipitation in highly basic aqueous solutions containing barium and zirconium salts. The effect of the hydroxide concentration was discussed in relation to the barium zirconate phase formation, the particles size and the particles size distribution. For each powder, microstructural characterisations have been performed on sintered bodies in order to evaluate the influence of the thermal treatment on the final density. Dilatometric measurements have been also performed in order to quantify the densification process. Important informations were obtained by these techniques, as for example the existence of an internal porosity which severely limits the final density of the material, even if sintering was performed at high temperature. Thus a careful control of the heating profile seems to be necessary in order to produce dense materials. [less ▲]

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